The present invention relates to a machine tool.
In particular, the present invention relates to a high/ultra-high speed machine tool for operations such as milling and drilling parts of notably large dimensions.
Machine tools of the type in question present a bridge-like structure commonly referred to as a gantry, and find application to advantage in the preparation of models or moulds for motor vehicles, by way of example, or in the fabrication of wings for aircraft, and such like.
More exactly, the prior art embraces machine tools furnished with two longitudinal and parallel slide ways supporting a gantry able to travel along a path parallel to the longitudinal axis of the selfsame slide ways.
The slide ways are normally spaced apart in such a manner that the space between them will serve as a machining station in which to position the work. The traveling gantry is composed of two upright members, each slidably associated with a respective way, whilst the uprights in turn are surmounted by a horizontal cross member or beam traversable over the machining station and carrying a machining head equippable with a corresponding tool for the type of work or part in process.
Generally speaking, the machining head is able to travel along the beam in a direction transverse to the direction of movement of the gantry. Moreover, the head can be raised from and lowered toward the machining station and is rotatable about two axes, the one vertical and the other transverse to the longitudinal axis of the slide ways, allowing the tool to be set at a given angle. The tool itself is also rotatable about a respective longitudinal axis in order to mill or drill the part.
Thus, the machining head is capable of movement referable to five axes: a longitudinal first axis extending parallel to the axis of the slide ways (movement of the gantry uprights along the slide ways); a second axis transverse to the longitudinal axis of the ways (movement of the machining head along the beam); a vertical third axis (movement of the head toward/away from the machining station); a vertical fourth axis of rotation (rotary movement of the head); and a fifth axis of rotation normal to the vertical fourth axis (pivoting movement of the head).
The part is positioned in the machining station, and the machining head maneuvered by the gantry in such a way as to engage the specified areas of the part.
In addition, the machining station is divided by a bulkhead establishing a first zone and a second zone. With this dual-zone arrangement, machining operations can be carried out on two different parts, each occupying one of the aforementioned zones.
When carrying out operations on aircraft wings, for example, each wing is placed in a corresponding zone and the gantry then made to position the head over the two zones in alternation so that identical operations can be performed symmetrically on the two wings.
Also embraced by the prior art are machine tools presenting slide ways mounted to respective side walls, and equipped with a tool magazine positioned alongside one of the side walls.
The magazine appears as a chamber internally of which to accommodate a plurality of tools, each one designed to perform a particular operation.
The magazine is also connected to the machining station by way of a mechanical changer arm. More exactly, the arm is positioned to coincide with an opening in the relative side wall, placed to allow communication between the machining station and the chamber of the magazine.
With this type of arrangement, the tools held by the machining head can be changed automatically. In particular, whenever a tool currently in use needs to be changed, the gantry is directed to a point alongside the aforementioned opening, whereupon the changer arm will grip and remove the tool from the head and return it to the magazine. Thereafter, a new tool is taken by the changer from the magazine and offered to the machining head.
The magazine can also be equipped with a gripper device capable of movement within the chamber, such as will select and lay hold on a tool and position it on the changer arm.
In this way, the steps of selecting and changing tools can be fully automated.
Nonetheless, a machine tool of the conventional type thus outlined presents a drawback connected with the tool change operations.
In effect, it will be observed that the opening and therefore the mechanical changer arm are placed in one of the two zones of the machining station. Accordingly, when the machining head happens to be operating in the zone opposite to that occupied by the changer arm, the gantry must travel from one zone to the other in order to make the change.
As a result, machining times are prolonged due to the continuous movements of the gantry required in order to carry out tool changes. These machining times will be even longer if the distance between the tool change opening and the zone currently occupied by the machining head is especially great.
A further drawback with the arrangement described is that it prevents an operator from entering and attending to a part occupying the first zone, for example, even when the gantry is positioned over a part occupying the second zone.
This drawback derives, similarly, from the fact that the gantry has to travel continually between the first and second zones in order to carry out machining and tool change operations. In practice, therefore, the operator cannot rely on sufficiently safe working conditions in which to work on a part, since even if no machining operations are taking place in the relative zone at any given moment, the gantry may still travel into this idle zone.
There are also prior art machine tools in which these drawbacks are overcome by duplicating all of the components involved in tool change operations. More exactly, such machines have: two magazines, each one positioned alongside a relative zone; two openings afforded by a relative side wall, allowing each magazine to communicate with the corresponding zone; and two mechanical changer arms, one for each magazine.
In this solution, all the machining tools held in the magazines are likewise duplicated.
The gantry can therefore machine and change tools while remaining in the same zone, without having to travel continually, and the adjacent zone is left free for manual operations if need be.
It will be appreciated that this solution, while not affected by the problems mentioned previously, presents a major drawback of structural complexity attributable to the inclusion of two magazines.
Moreover, this solution is penalized by an unduly high cost of implementation, again attributable to the fact that all components involved in the tool change operation are duplicated.
The object of the present invention is to provide a machine tool unaffected by the aforementioned drawbacks.
One object of the invention, in particular, is to set forth a machine tool equipped with tool change components that are accessible from both zones of the machining station.
A further object of the invention is to provide an economical machine tool with a simple structure.